废弃人造板氮含量高，热转化处理与应用存在NO_x污染问题。重点研究纤维板水热转化过程中氮在固液两相的迁移与转化，分析了水热热转化温度及停留时间对氮在固液两相的分布与转化的影响，对氮迁移转化路径与机理进行了探讨。结果表明，纤维板中的外源氮在水热转化过程中易向液相迁移，140 ℃水热转化0 min仅有约10%氮保留在固相中。进一步提升水热温度，部分液相氮迁移回固相中。水热温度提升到220 ℃前，氮在固相中的固集作用随温度提升显著增强，分析认为主要是半纤维与纤维素水解的富含氧官能团的中间产物强化了氮固集的Maillard反应。260 ℃水热条件下，长停留时间促进了木质纤维素水解产物在固相中的缩聚，液相游离氮也广泛参与了此反应过程，由此氮的固集作用被显著增强。低温水热条件下固相氮以胺氮为主，水热温度达到180 ℃后，缩合、聚合以及芳构化作用的增强使固相中氮转变为杂环氮，水热温度的进一步提升使杂环氮向更稳定的结构转化。同时，高温水热固相产物中胺氮始终保持一定份额，验证了液相游离氮在固相中固集作用的发生。对应固相氮的迁移，液相氮含量在140 ℃达到最大值，此后随着温度的提升其含量一直保持下降趋势。液相氮以有机氮和铵氮为主，液相氮的转变由有机氮去氨基化反应和Maillard反应共同影响。低温水热条件下，提升温度导致去氨基化反应增强使铵氮含量有增加趋势，高温条件Maillard反应的增强又使部分铵氮返回到有机结构中。有机氮测试分析表明，低温水热下液相氮的结构主要以聚合度较高的大分子结构为主，180 ℃条件下开始有大量的挥发性杂环氮生成，且吡啶氮一直是有机氮的主要结构成分。

The high content of nitrogen in the waste wood-based panels will result in NO_x pollution during their thermochemical conversions. This study focused on the nitrogen migration and transformation in the solid and aqueous products during hydrothermal conversion (HTC) of fiberboard. The effect of HTC temperatures and residence times on the distribution and conversion of nitrogen in the solid and aqueous products were investigated, and the conversion pathway and mechanisms were discussed. Results indicated that the exogenous nitrogen in the fiberboard could easily migrate into an aqueous phase during HTC, with only ~10% nitrogen kept in the solid phase at the HTC temperature of 140 ℃ and the residence time of 0. Further increase of HTC temperatures, some of the aqueous nitrogen migrated back to the solid phase. Nitrogen fixing ratios in the solid phase increased significantly with the rising HTC temperature until 220 ℃. This was mainly caused by the Maillard reactions for nitrogen fixation strengthened by the oxygen-rich intermediates generated from the hydrolysis of hemicellulose and cellulose. At the HTC temperature of 260 ℃, long residence times were favorable of the condensation and polymerization of intermediates hydrolyzed from lignocellulose, in which the free nitrogen in the liquid phase was also involved. Thus, the nitrogen fixation was obviously enhanced. In lower HTC temperatures, amine-N dominated the nitrogen in the solid phase. When the temperature reached 180 ℃, the nitrogen in the solid phase was converted into heterocyclic-N by the boosted condensation, polymerization, and aromatization reactions. Further increase of HTC temperatures changed the heterocyclic-N to be more thermostable. Meanwhile, amine-N remained a certain proportion in the solid products at higher temperatures, which verified that a part of nitrogen in the liquid phase was re-fixed in the solid phase. The content of aqueous nitrogen reached a maximum at 140 ℃, which corresponded to the minimum nitrogen content in the solid products at this temperature. Further increasing the temperatures, the content of aqueous nitrogen kept decreasing. Organic-N and ammonium-N were the main nitrogen species in the aqueous phase, and the changes of aqueous nitrogen were determined by deamination and Maillard reactions. At lower HTC temperatures, the increase of temperatures enhanced the deamination reaction and thus promoted the generation of ammonium-N. While at higher temperatures, the enhancement of Maillard reaction converted a part of ammonium-N to organic-N again. Testing on the organic-N showed that the structure of nitrogen in the aqueous phase at lower HTC temperatures was mainly large molecular structure with a high degree of polymerization. Increasing the temperature to 180 ℃ could trigger the massive formation of volatile heterocyclic-N, and the pyridine-N kept accounting for the dominant proportion of organic-N.